Poly lactic acid-containing film or sheet, and method for manufacturing thereof

ABSTRACT

Provided are a film or sheet composed of a resin composition that includes a poly lactic acid (A), an acidic functional group-modified olefinic polymer (B) including an acidic functional group and having an acid value of 10 to 70 mg KOH/g and a weight average molecular weight of 10,000 to 80,000, a tetrafluoroethylene polymer (C), and a dicarboxylic acid ester-containing plasticizer (D) containing a compound of General Formula (1) and in which the dicarboxylic acid ester-containing plasticizer (D) is included in an amount of 8 parts by weight or more and less than 40 parts by weight based on 100 parts by weight of the poly lactic acid (A), and a method for manufacturing the film or sheet by melt film formation. Each sign in Formula is as described in the specification.

TECHNICAL FIELD

The present invention relates to poly lactic acid-containing films orsheets that have heat resistance and roll lubricity as well as excellentflexibility.

BACKGROUND ART

A poly lactic acid resin is a biomass polymer and therefore has beendrawing attention in recent years against the background of thedepletion of petroleum resources, the reduction of carbon dioxideemissions, and the like.

However, the poly lactic acid has a low crystallization rate and isunlikely to be crystallized by a common film forming procedure. Hence, afilm composed of a resin composition containing the poly lactic acid hasa problem of poor heat resistance. For example, such a film is thermallydeformed at about 60° C. or more that is a glass transition temperatureof the poly lactic acid and cannot keep a film shape.

The addition of a plasticizer and the like is a known method forimproving brittleness of the poly lactic acid.

However, commonly, the addition of a plasticizer having goodcompatibility with the poly lactic acid lowers a glass transitiontemperature of the poly lactic acid, and the heat resistance of the filmis often further lowered than that of a film containing poly lactic acidalone. Thus, such a film is difficult to be used at the glass transitiontemperature or more.

Patent Document 1 discloses a method for improving the heat resistancein which poly lactic acid including a plasticizer is molded at atemperature between the glass transition temperature and the meltingpoint to improve the heat resistance. However, there is no descriptionabout the specific time required for crystallization, and it is unknownwhether a film can be continuously formed at a practicable speed.

There is also disclosed a method for obtaining a molded article that hasgood injection molding properties (time required for molding), a highVicat softening point (high heat resistance), and flexibility by addinga plasticizer, polyalkylene glycol, and a styrene copolymer to the polylactic acid (Patent Document 2).

However, the method requires a large amount of the styrene copolymer toremarkably reduce biomass degree. Moreover, such a molded article has alow heat resistance at about 80° C. and does not have a heat resistanceapplicable for heat-resistant parts in home electric appliances orautomobiles.

There is disclosed another method of crystallization by adding aparticular plasticizer and a crystal nucleating agent to poly lacticacid to give a mixture, forming a film from the mixture with anextruder, once cooling the film, and then passing the film through aprocess from 60 to 100° C. (Patent Document 3).

However, the method is inefficient because a film is once cooled andsolidified, and then heated again.

There is another problem. That is, when a resin composition containingthe poly lactic acid is melted to form a film or sheet using metalrolls, the resin composition adheres to the metal rolls to interferewith the formation of the film or sheet because the resin compositionhas a poor releasability from the rolls.

CITATION LIST Patent Literature

Patent Document 1: Japanese Patent No. 3865960

Patent Document 2: Japanese Unexamined Patent Application No.2007-177213

Patent Document 3: Japanese Patent No. 4246196

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide a poly lacticacid-containing film or sheet having excellent heat resistance bymaintaining high crystallizability and having flexibility and a methodfor manufacturing the film and sheet.

Solution to Problem

The present inventors have carried out intensive studies to solve theproblems, and as a result, have found that a film or sheet having heatresistance and flexibility can be obtained by using a particulardicarboxylic acid ester-containing plasticizer that melts in atemperature range where poly lactic acid is melted and kneaded forachieving flexibility and by adding a tetrafluoroethylene polymer forimproving the crystallizability of poly lactic acid, and the inventionhas been accomplished.

That is, the present invention is as described below.

[1] A film or sheet is composed of a resin composition that includes apoly lactic acid (A), an acidic functional group-modified olefinicpolymer (B) including an acidic functional group and having an acidvalue of 10 to 70 mg KOH/g and a weight average molecular weight of10,000 to 80,000, a tetrafluoroethylene polymer (C), and a dicarboxylicacid ester-containing plasticizer (D) of General Formula (1). Thedicarboxylic acid ester-containing plasticizer (D) is included in anamount of 8 parts by weight or more and less than 40 parts by weightbased on 100 parts by weight of the poly lactic acid (A).

(Where B is a 1,2-phenylene group or —CH₂(CH₂)_(m)CH₂— (where m is aninteger of 0 to 6), each of Aa and Ab is independently selected from (1)to (3) (where a compound in which both Aa and Ab are (3) is excluded):(1) C₆H₅—(Ac)— (where Ac is an alkylene group having 1 to 4 carbonatoms); (2) (Ae)-(Ad-O)_(n)— (where Ad is an alkylene group having 1 to5 carbon atoms, Ae is an alkyl group having 1 to 7 carbon atoms, and nis an integer of 1 to 4); and (3) an alkyl group having 1 to 14 carbonatoms)

[2] In the film or sheet according to the aspect [1], the dicarboxylicacid ester-containing plasticizer (D) is a phthalate ester-containingplasticizer (DP) selected from compounds of General Formulae (2) to (6),and the phthalate ester-containing plasticizer (DP) is included in anamount of 10 parts by weight or more and less than 40 parts by weightbased on 100 parts by weight of the poly lactic acid (A).

(Where A1 and A2 are the same or different from each other; each of A1and A2 is an alkylene group having 1 to 4 carbon atoms; A3 is an alkylgroup having 1 to 14 carbon atoms; A4 is an alkylene group having 1 to 5carbon atoms; A5 is an alkyl group having 1 to 7 carbon atoms; and n isan integer of 1 to 4)

[3] In the film or sheet according to the aspect [1], the dicarboxylicacid ester-containing plasticizer (D) is an aliphatic dicarboxylic acidester-containing plasticizer (DA) selected from compounds of GeneralFormulae (7) to (11), and the aliphatic dicarboxylic acidester-containing plasticizer (DA) is included in an amount of 8 to 35parts by weight based on 100 parts by weight of the poly lactic acid(A).

(Where A1 and A2 are the same or different from each other; each of A1and A2 is an alkylene group having 1 to 4 carbon atoms; A3 is an alkylgroup having 1 to 14 carbon atoms; A4 is an alkylene group having 1 to 5carbon atoms; A5 is an alkyl group having 1 to 7 carbon atoms; n is aninteger of 1 to 4; and m is an integer of 0 to 6)

[4] In the film or sheet according to any one of the aspects [1] to [3],the acidic functional group included in the acidic functionalgroup-modified olefinic polymer (B) is a carboxylic acid anhydridegroup.

[5] In the film or sheet according to any one of the aspects [1] to [4],the tetrafluoroethylene polymer (C) is included in an amount of 0.5 to15.0 parts by weight based on 100 parts by weight of the poly lacticacid (A).

[6] In the film or sheet according to any one of the aspects [1] to [5],the acidic functional group-modified olefinic polymer (B) is included inan amount of 0.1 to 10.0 parts by weight based on 100 parts by weight ofthe poly lactic acid (A).

[7] In the film or sheet according to any one of the aspects [1] to [6],the resin composition further includes a crystallization accelerator(E), and the crystallization accelerator (E) is included in an amount of0.1 to 5.0 parts by weight based on 100 parts by weight of the polylactic acid (A).

[8] The film or sheet according to any one of the aspects [1] to [7] hasa deformation rate of 40% or less under a load of 10 N for 30 minutes ina temperature environment of 120° C. in accordance with heat deformationtest in Japanese Industrial Standard C3005, and has a relativecrystallization rate of 50% or more calculated from Equation (I)

Relative crystallization rate (%)=(ΔHm−ΔHc)/ΔHm×100   (I)

(where ΔHc is an amount of heat of an exothermic peak associated withcrystallization of the film or sheet in a temperature rise process afterfilm formation, and ΔHm is an amount of heat associated with melting).

[9] The film or sheet according to any one of the aspects [1] to [8] hasa tensile elongation at break of 100% or more and a residual stressratio of 40% or less at a stretch of 10%.

[10] A method for manufacturing the film or sheet according to any oneof the aspects [1] to [9] includes forming a film from a resincomposition by melt film formation. In the method, the resin compositionduring the melt film formation has a temperature between a temperature15° C. higher than a crystallization temperature (Tc) of the resincomposition in a temperature drop process and a temperature 5° C. lowerthan a melting temperature (Tm) in a temperature rise process, or themelt film formed resin composition is cooled and solidified after acrystallization accelerating step between a temperature 25° C. lowerthan a crystallization temperature (Tc) of the resin composition in atemperature drop process and a temperature 10° C. higher than thecrystallization temperature (Tc).

[11] In the method for manufacturing the film or sheet according to theaspect [10], the resin composition during the melt film formation has atemperature between a temperature 15° C. higher than a crystallizationtemperature (Tc) of the resin composition in a temperature drop processand a temperature 5° C. lower than a melting temperature (Tm) in atemperature rise process, and the melt film formed resin composition iscooled and solidified after a crystallization accelerating step betweena temperature 25° C. lower than a crystallization temperature (Tc) ofthe resin composition in a temperature drop process and a temperature10° C. higher than the crystallization temperature (Tc).

[12] In the method for manufacturing the film or sheet according to theaspect [10] or [11], the melt film formation is a technique of forming afilm having a desired thickness by passing the melted resin compositionthrough a space between two metal rolls.

[13] In the method for manufacturing the film or sheet according to anyone of the aspects [10] to [12], the crystallization accelerating stepis performed by using a metal roll.

Advantageous Effects of Invention

According to the present invention, a poly lactic acid-containing filmor sheet having roll lubricity and flexibility can be provided whilemaintaining excellent heat resistance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a calender film formation machine.

FIG. 2 is a schematic view of a polishing film formation machine.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described in detail.

The film or sheet of the present invention is composed of a resincomposition that includes a poly lactic acid (A), an acidic functionalgroup-modified olefinic polymer (B), a tetrafluoroethylene polymer (C),and a dicarboxylic acid ester-containing plasticizer (D). The film orsheet of the present invention includes a transparent film or sheet, atranslucent film or sheet, and an opaque film or sheet.

The thickness of the film or sheet of the present invention is notnecessarily limited, but is commonly 10 to 500 μm, preferably 20 to 400μm, and more preferably 30 to 300 μm.

[Poly Lactic Acid (A)]

Lactic acid that is a material monomer of the poly lactic acid includesL- and D-optical isomers due to its asymmetric carbon atom. The polylactic acid (A) used in the present invention is a polymer mainlycomposed of L-lactic acid. A polymer containing a smaller amount ofD-lactic acid as an impurity during the manufacture has a highercrystallinity and a higher melting point. Hence, lactic acid to be usedpreferably has an L-lactic acid purity as high as possible, and thepurity of L-lactic acid is more preferably 95% or more. The poly lacticacid (A) used in the present invention may include other copolymerizablecomponents in addition to the lactic acid. Examples of other monomerunits include glycol compounds such as ethylene glycol, propyleneglycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol,decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin,pentaerythritol, bisphenol A, polyethylene glycol, polypropylene glycol,and polytetramethylene glycol; dicarboxylic acids such as oxalic acid,adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonicacid, glutaric acid, cyclohexanedicarboxylic acid, terephthalic acid,isophthalic acid, phthalic acid, naphthalenedicarboxylic acid,bis(p-carboxyphenyl)methane, anthracenedicarboxylic acid, 4,4′-diphenylether dicarboxylic acid, 5-sodium sulfoisophthalic acid, and5-tetrabutylphosphonium isophthalic acid; hydroxycarboxylic acids suchas glycolic acid, hydroxypropionic acid, hydroxybutyric acid,hydroxyvaleric acid, hydroxycaproic acid, and hydroxybenzoic acid; andlactones such as caprolactone, valerolactone, propiolactone,undecalactone, and 1,5-oxepan-2-one. The content of such an othercopolymerizable component is preferably 0 to 30% by mol and preferably 0to 10% by mol based on the total monomer components.

The weight average molecular weight of the poly lactic acid (A) is, forexample, 10,000 to 400,000, preferably 50,000 to 300,000, and morepreferably 80,000 to 150,000. The melt flow rate of the poly lactic acid(A) at 190° C. under a load of 21.2 N [Japanese Industrial StandardK-7210 (test condition 4)] is, for example, 0.1 to 50 g/10 minutes,preferably 0.2 to 20 g/10 minutes, more preferably 0.5 to 10 g/10minutes, and particularly preferably 1 to 7 g/10 minutes. The polylactic acid (A) having a too high melt flow rate may form a film orsheet having poor mechanical characteristics and heat resistance. Thepoly lactic acid (A) having a too low melt flow rate may lead to a toohigh load during film formation.

In the specification, the “weight average molecular weight” means thatdetermined by gel permeation chromatography (GPC) (in terms ofpolystyrene). Conditions for GPC are as described below.

Column: TSKgel SuperHZM-H/HZ2000/HZ1000

Column size: 4.6 mm ID×150 mm

Eluant: chloroform

Flow rate: 0.3 ml/min

Detector: RI

Column temperature: 40° C.

Injection volume: 10 μl

The method for producing the poly lactic acid is not necessarily limitedand typical examples of the production method include lactide method anddirect polymerization method. The lactide method is as follows: lacticacid is heated and dehydrocondensed to give poly lactic acid having alow molecular weight; the poly lactic acid is heated and decomposedunder reduced pressure to give lactide that is a cyclic dimer of lacticacid; and the lactide is ring-opening polymerized in the presence of ametal salt catalyst such as tin(II) octanoate to give poly lactic acidhaving a high molecular weight. The direct polymerization method is asfollows: lactic acid is heated in a solvent such as diphenyl ether underreduced pressure to be polymerized while removing water in order tosuppress hydrolysis to give poly lactic acid directly.

A commercial product may be used as the poly lactic acid (A). Examplesof the commercial product include trade names “Lacea H-400” and “LaceaH-100” (manufactured by Mitsui Chemicals, Inc.) and trade names“Terramac TP-4000” and “Terramac TE-4000” (manufactured by UnitikaLtd.). A poly lactic acid (A) produced by a known or commonpolymerization method (for example, emulsion polymerization and solutionpolymerization) may be also used.

[Acidic Functional Group-Modified Olefinic Polymer (B)]

The manufacture of the film or sheet of the present invention requiresthe film formation by passing the melted poly lactic acid (A)-containingresin composition through a space between metal rolls with, for example,a calender film formation machine. Thus, the resin composition must bereadily removed from the metal roll surfaces. The acidic functionalgroup-modified olefinic polymer (B) included in the film or sheet of thepresent invention works as a lubricant to give a desired roll lubricity(that is, releasability form a roll) to the poly lactic acid(A)-containing resin composition.

Examples of the acidic functional group of the acidic functionalgroup-modified olefinic polymer (B) include a carboxyl group and groupsderived from it. The group derived form the carboxyl group is chemicallyderived from the carboxyl group, and examples include a carboxylic acidanhydride group, an ester group, an amide group, an imide group, and acyano group. The carboxylic acid anhydride group is preferred.

The acidic functional group-modified olefinic polymer (B) is obtainedby, for example, graft polymerization of an unmodified polyolefinpolymer with an unsaturated compound containing the “acidic functionalgroup” (hereinafter, also abbreviated to an acidic functionalgroup-containing unsaturated compound).

Examples of the unmodified polyolefin polymer include polymers includingpolyolefins such as high-density polyethylene, medium-densitypolyethylene, low-density polyethylene, polypropylene, polybutene,poly-4-methylpentene-1, a copolymer of ethylene and α-olefin, and acopolymer of propylene and α-olefin and oligomers of them; polyolefinelastomers such as ethylene-propylene rubber, ethylene-propylene-dienecopolymer rubber, butyl rubber, butadiene rubber, a low-crystallineethylene-propylene copolymer, a propylene-butene copolymer, anethylene-vinyl ester copolymer, an ethylene-methyl(meth)acrylatecopolymer, an ethylene-ethyl(meth)acrylate copolymer, an ethylene-maleicanhydride copolymer, and a blend of polypropylene and ethylene-propylenerubber; and a mixture of two or more of them. Preferred arepolypropylene, a copolymer of propylene and α-olefin, low-densitypolyethylene, and oligomers of them, and particularly preferred arepolypropylene, a copolymer of propylene and α-olefin, and oligomers ofthem. Examples of the “oligomers” include compounds obtained from acorresponding polymer by thermal decomposition in accordance withmolecular weight reduction method. Such oligomers can also be obtainedby polymerization.

Examples of the acidic functional group-containing unsaturated compoundinclude a carboxyl group-containing unsaturated compound and anunsaturated compound containing a group derived from a carboxyl group.Examples of the carboxyl group-containing unsaturated compound includemaleic acid, itaconic acid, chloroitaconic acid, chloromaleic acid,citraconic acid, and (meth)acrylic acid. Examples of the unsaturatedcompound containing a group derived from a carboxyl group includecarboxylic acid anhydride group-containing unsaturated compounds such asmaleic anhydride, itaconic anhydride, chloroitaconic anhydride,chloromaleic anhydride, and citraconic anhydride; (meth)acrylic acidesters such as methyl(meth)acrylate, glycidyl(meth)acrylate, and2-hydroxyethyl (meth)acrylate; and (meth)acrylamide, maleimide, and(meth)acrylonitrile. Preferred are carboxyl group-containing unsaturatedcompounds and carboxylic acid anhydride group-containing unsaturatedcompounds, more preferred are carboxylic acid anhydride group-containingunsaturated compounds, and maleic anhydride is even more preferred.

Importantly, the acidic functional group-modified olefinic polymer (B)has a weight average molecular weight of 10,000 to 80,000, preferably15,000 to 70,000, and more preferably 20,000 to 60,000. The polymerhaving a weight average molecular weight of less than 10,000 causesbleed out after the formation of the film or sheet, and the polymerhaving a weight average molecular weight of more than 80,000 leads toseparation of the polymer from the poly lactic acid during rollkneading. Here, the bleed out means the phenomenon of bleeding of a lowmolecular weight component out to the surface of a film or sheet withtime after the film or sheet formation. In the specification, the“weight average molecular weight” means that determined by gelpermeation chromatography (GPC).

The acidic functional group in the acidic functional group-modifiedolefinic polymer (B) may be bonded to any position in the olefinicpolymer. The modified ratio is not necessarily limited, but the acidicfunctional group-modified olefinic polymer (B) commonly has an acidvalue of 10 to 70 mg KOH/g and preferably 20 to 60 mg KOH/g. The polymerhaving an acid value of less than 10 mg KOH/g cannot improve the rolllubricity, and the polymer having an acid value of more than 70 mg KOH/gcauses plate out to a roll. Here, the plate out to a roll means adheringor depositing of a component contained in the resin composition, anoxidation, decomposition, combination, or degradation product of thecomponent, or the like to a metal roll surface during the melt filmformation of the resin composition using the metal roll. In thespecification, the “acid value” means that determined by neutralizationtitration in accordance with Japanese Industrial Standard K0070-1992.

The acidic functional group-modified olefinic polymer (B) is obtained byreaction of the acidic functional group-containing unsaturated compoundand the unmodified polyolefin polymer in the presence of an organicperoxide. The organic peroxide to be used may be an initiator that iscommonly used for radical polymerization. Such reaction may be carriedout by either solution process or melting process.

In the solution process, a mixture of the unmodified polyolefin polymerand the acidic functional group-containing unsaturated compound isdissolved in an organic solvent together with an organic peroxide, andthe solution is heated to give the acidic functional group-modifiedolefinic polymer (B). The reaction temperature is preferably about 110to 170° C.

In the melting process, a mixture of the unmodified polyolefin polymerand the acidic functional group-containing unsaturated compound is mixedwith an organic peroxide, and the whole is melted and mixed for reactionto give the acidic functional group-modified olefinic polymer (B). Themelt-mixing can be carried out with various mixers such as an extruder,a Brabender, a kneader, and a Banbury mixer, and the kneadingtemperature is commonly from a melting point of the unmodifiedpolyolefin polymer to 300° C.

The acidic functional group-modified olefinic polymer (B) is preferablya maleic anhydride group-modified polypropylene. For the acidicfunctional group-modified olefinic polymer (B), commercial products maybe used, and examples include “Umex (registered trademark) 1010” (maleicanhydride group-modified polypropylene, acid value: 52 mg KOH/g, weightaverage molecular weight: 32,000, modified ratio: 10% by weight), “Umex(registered trademark) 1001” (maleic anhydride group-modifiedpolypropylene, acid value: 26 mg KOH/g, weight average molecular weight:49,000, modified ratio: 5% by weight), and “Umex (registered trademark)2000” (maleic anhydride group-modified polyethylene, acid. value: 30 mgKOH/g, weight average molecular weight: 20,000, modified ratio: 5% byweight), each manufactured by Sanyo Chemical Industries, Ltd.

The content of the acidic functional group-modified olefinic polymer (B)is not necessarily limited and commonly 0.1 to 10.0 parts by weightbased on 100 parts by weight of the poly lactic acid (A). The content ispreferably 0.1 to 5.0 parts by weight and particularly preferably 0.3 to3.0 parts by weight in order to continue the roll lubricity effectwithout plate out to a roll and to maintain the biomass degree. Thepolymer having a content of less than 0.1 part by weight is unlikely toimprove the roll lubricity, and the polymer having a content of morethan 10.0 parts by weight cannot achieve effects corresponding to theamount added and reduces the biomass degree. Here, the biomass degreemeans the ratio of the dry weight of biomass used to the dry weight ofthe film or sheet. The biomass means renewable organic resources derivedfrom biological materials except for fossil resources.

[Tetrafluoroethylene Polymer (C)]

The tetrafluoroethylene polymer (C) included in the film or sheet of thepresent invention can improve the melt tension of the poly lactic acid(A)-containing resin composition and achieve oriented crystallization ina flow field in the melt film formation process to accelerate thecrystallization of the poly lactic acid (A). The tetrafluoroethylenepolymer (C) also works as a crystal nucleating agent for the poly lacticacid (A). Hence, the temperature setting of the resin compositionimmediately after the film formation to around a crystallizationtemperature can further accelerate the crystallization of the polylactic acid (A). Thus, the tetrafluoroethylene polymer (C) acceleratesthe crystallization of the poly lactic acid (A) and therefore canprovide heat resistance to the film or sheet of the present invention.

The tetrafluoroethylene polymer (C) used in the present invention is ahomopolymer of tetrafluoroethylene or a copolymer of tetrafluoroethyleneand another monomer, and examples include polytetrafluoroethylene,perfluoroalkoxyalkane (a copolymer of tetrafluoroethylene andperfluoroalkyl vinyl ether), a perfluoroethylene propene copolymer (acopolymer of tetrafluoroethylene and hexafluoropropylene), anethylene-tetrafluoroethylene copolymer (a copolymer oftetrafluoroethylene and ethylene), and a copolymer oftetrafluoroethylene and perfluorodioxole. Polytetrafluoroethylene ispreferred.

It is supposed that the effect of the tetrafluoroethylene polymer (C) asa crystal nucleating agent on the poly lactic acid (A) depends on thecrystal structure of the tetrafluoroethylene polymer (C). Wide anglex-ray diffraction revealed that the poly lactic acid (A) had a crystallattice having an interplanar spacing of 4.8 angstroms while thetetrafluoroethylene polymer had a crystal lattice having an interplanarspacing of 4.9 angstroms. The results suggest that thetetrafluoroethylene polymer (C) can work as the crystal nucleating agentfor the poly lactic acid (A) due to an epitaxial effect. Here, theepitaxis means the crystal growth of the poly lactic acid (A) that isaligned with the crystal face on the crystal surface of thetetrafluoroethylene polymer (C) in the crystal growth of the poly lacticacid (A) on the surface of the tetrafluoroethylene polymer (C).

The tetrafluoroethylene polymer (C) has the same interplanar spacing asthat of a copolymer of tetrafluoroethylene and another monomer becausethe interplanar spacing depends on the crystal form of thetetrafluoroethylene moiety. Hence, as long as the crystal form of thepolytetrafluoroethylene is maintained and the physical properties arenot greatly changed, the amount of another monomer component in thecopolymer is not specifically limited, but other monomer components arecommonly preferably included in an amount of 5% by weight or less in thetetrafluoroethylene polymer (C).

The polymerization method of the tetrafluoroethylene polymer (C) is notnecessarily limited but is specifically preferably emulsificationpolymerization. The tetrafluoroethylene polymer (C) obtained through theemulsification polymerization is readily fibrillated to readily form anetwork structure in the poly lactic acid (A). Then, this is supposed toimprove the melt tension of the resin composition including the polylactic acid (A) and to effectively accelerate the crystallization of thepoly lactic acid (A) in the flow field in the melt film formationprocess.

The weight average molecular weight of the tetrafluoroethylene polymer(C) is not necessarily limited, and commonly 1,000,000 to 10,000,000 andpreferably 2,000,000 to 8,000,000.

Furthermore, for uniform dispersion in the poly lactic acid (A),particles of the “tetrafluoroethylene polymer (C)” may be modified witha polymer having high affinity to the poly lactic acid (A), such as a(meth)acrylic acid ester polymer. Examples of such a tetrafluoroethylenepolymer (C) include acrylic-modified polytetrafluoroethylene.

Commercially available tetrafluoroethylene polymers (C) may be used, andexamples of the commercially available polytetrafluoroethylene include“Fluon (registered trademark) CD-014”, “Fluon (registered trademark)CD-1”, and “Fluon (registered trademark) CD-145” manufactured by ASAHIGLASS CO., LTD. Examples of the commercially available acrylic-modifiedpolytetrafluoroethylene include Metablen (registered trademark), seriesA (for example, A-3000 and A-3800) manufactured by Mitsubishi Rayon Co.,Ltd.

The content of the tetrafluoroethylene polymer (C) is commonly 0.5 to15.0 parts by weight based on 100 parts by weight of the poly lacticacid (A). The content is preferably 0.7 to 10.0 parts by weight andparticularly preferably 1.0 to 5.0 parts by weight in order to improvethe melt tension, to maintain the biomass degree, and to obtain a goodsurface condition. The polymer having a content of less than 0.5 part byweight is unlikely to improve the melt tension, and the polymer having acontent of more than 15.0 parts by weight cannot achieve effectscorresponding to the amount added and reduces the biomass degree.

[Dicarboxylic Acid Ester-Containing Plasticizer (D)]

The dicarboxylic acid ester-containing plasticizer (D) included in thefilm or sheet of the present invention has an effect as a plasticizer toprovide desired flexibility to the resin composition including the polylactic acid (A). The dicarboxylic acid ester-containing plasticizer (D)includes a compound represented by General Formula (1).

(Where B is a 1,2-phenylene group or —CH₂(CH₂)_(m)CH₂— (where m is aninteger of 0 to 6); each of Aa and Ab is independently selected from (1)to (3) (where a compound in which both Aa and Ab are (3) is excluded):(1) C₆H₅—(Ac)— (where Ac is an alkylene group having 1 to 4 carbonatoms); (2) (Ae)-(Ad-O)_(n)— (where Ad is an alkylene group having 1 to5 carbon atoms, Ae is an alkyl group having 1 to 7 carbon atoms, and nis an integer of 1 to 4); and (3) an alkyl group having 1 to 14 carbonatoms)

Hereinafter, the definition of each group in General Formula (1) will bedescribed in details.

Examples of the “alkylene group having 1 to 4 carbon atoms” representedby Ac include a methylene group, an ethylene group, a trimethylenegroup, and a tetramethylene group, and a methylene group is preferred.

Examples of the “alkylene group having 1 to 5 carbon atoms” representedby Ad include straight or branched alkylene groups such as a methylenegroup, an ethylene group, a trimethylene group, a propylene group, atetramethylene group, a 1,1′-dimethylethylene group, and apentamethylene group, and an ethylene group is preferred.

The “alkyl group having 1 to 7 carbon atoms” represented by Ae may be astraight or branched chain, and examples of the group include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, an isobutyl group, a sec-butyl group, a tent-butyl group, apentyl group, a 2-pentyl group, a 3-pentyl group, a neopentyl group, atert-pentyl group, a hexyl group, an isohexyl group, and a heptyl group.

The “alkyl group having 1 to 14 carbon atoms” means a straight orbranched saturated hydrocarbon group having 1 to 14 carbon atoms, andexamples of the group include a methyl group, an ethyl group, a propylgroup, an isopropyl group, a butyl group, an isobutyl group, a sec-butylgroup, a tert-butyl group, a pentyl group, an isopentyl group, aneopentyl group, a 1,2-dimethylpropyl group, a 1-ethylpropyl group, ahexyl group, an isohexyl group, a 1,2,2-trimethylpropyl group, a1,1-dimethylbutyl group, a 2,2-dimethylbutyl group, a 3,3-dimethylbutylgroup, a 2-ethylbutyl group, a heptyl group, an isoheptyl group, a2-ethylhexyl group, an octyl group, an isooctyl group, a nonyl group, anisononyl group, a decyl group, an isodecyl group, an undecyl group, anisoundecyl group, a dodecyl group, an isododecyl group, a tridecylgroup, an isotridecyl group, a tetradecyl group, and an isotetradecylgroup. Alkyl groups having 1 to 8 carbon atoms are preferred, and abutyl group and a 2-ethylhexyl group are more preferred.

m is an integer of 0 to 6, and m is preferably 2. n is an integer of 1to 4, and n is preferably 2.

Among the compounds represented by General Formula (1), a compound inwhich both Aa and Ab are alkyl groups having 1 to 14 carbon atoms is notincluded in the dicarboxylic acid ester-containing plasticizer (D) ofthe present invention. That is, at least one of Aa and Ab is required toinclude an aryl group such as a phenylene group or an oxyalkylene chainsuch as an oxyethylene chain. The dicarboxylic acid ester-containingplasticizer (D) of the present invention has high hydrolysis resistanceand low volatility. Thus, the catalytic hydrolysis by the poly lacticacid can be suppressed and a small amount of the plasticizer can provideflexibility to the poly lactic acid. In particular, a particularcombination amount can also provide stress relaxation property.Furthermore, the low volatility leads to good workability during filmformation to give a poly lactic acid-containing flexible film or sheethaving stable performance.

In contrast, a low molecular weight plasticizer in which both Aa and Abinclude no aryl group or no oxyalkylene chain has a large plasticizationeffect and can provide flexibility even when it is included in a smallamount. However, it has large volatility at a processing temperature ofthe poly lactic acid (about 150 to 180° C.), hence the workingenvironment is deteriorated, and the included plasticizer does notremain in the film to lead to unstable performance.

The dicarboxylic acid ester-containing plasticizer (D) included in thefilm or sheet of the present invention is preferably a phthalateester-containing plasticizer (DP) that is selected from compounds ofGeneral Formulae (2) to (6).

Where A1 and A2 may be the same or different from each other; each of A1and A2 is an alkylene group having 1 to 4 carbon atoms; A3 is an alkylgroup having 1 to 14 carbon atoms; A4 is an alkylene group having 1 to 5carbon atoms; and A5 is an alkyl group having 1 to 7 carbon atoms. n isan integer of 1 to 4.

The “alkylene group having 1 to 4 carbon atoms”, the “alkylene grouphaving 1 to 5 carbon atoms”, the “alkyl group having 1 to 7 carbonatoms”, and the “alkyl group having 1 to 14 carbon atoms” are as definedabove.

Specific examples of the compound represented by General Formulae (2) to(6) include ethyl benzyl phthalate, butyl benzyl phthalate,(2-ethylhexyl)benzyl phthalate, (2-ethylhexyl)butyl diglycol phthalate,butyl(ethyl diglycol)phthalate, bis(butyl diglycol)phthalate, andbenzyl(butyl diglycol)phthalate.

The dicarboxylic acid ester-containing plasticizer (D) included in thefilm or sheet of the present invention is preferably an aliphaticdicarboxylic acid ester-containing plasticizer (DA) that is selectedfrom compounds of General Formulae (7) to (11).

Where A1 and A2 may be the same or different from each other; each of A1and A2 is an alkylene group having 1 to 4 carbon atoms; A3 is an alkylgroup having 1 to 14 carbon atoms; A4 is an alkylene group having 1 to 5carbon atoms; and A5 is an alkyl group having 1 to 7 carbon atoms. n isan integer of 1 to 4, and m is an integer of 0 to 6.

The “alkylene group having 1 to 4 carbon atoms”, the “alkylene grouphaving 1 to 5 carbon atoms”, the “alkyl group having 1 to 7 carbonatoms” and the “alkyl group having 1 to 14 carbon atoms” are as definedabove.

Specific examples of the compound represented by General Formulae (7) to(11) include (2-ethylhexyl)benzyl adipate, butyl benzyl adipate,(2-ethylhexyl)benzyl azelate, (2-ethylhexyl)benzyl sebacate,(2-ethylhexyl)butyl diglycol adipate, benzyl(methoxyethoxyethyl)adipate,bis(butyl diglycol)adipate, and bis[2-(2-butoxyethoxy)ethyl]adipate.

As described above, the dicarboxylic acid ester-containing plasticizer(D) includes the phthalate ester-containing plasticizer (DP) and thealiphatic dicarboxylic acid ester-containing plasticizer (DA).

The content of the dicarboxylic acid ester-containing plasticizer (D) ispreferably 8 parts by weight or more and less than 40 parts by weightbased on 100 parts by weight of the poly lactic acid (A). Among them,the content of the phthalate ester-containing plasticizer (DP) iscommonly 10 parts by weight or more and less than 40 parts by weight,preferably 12 parts by weight or more and less than 40 parts by weight,and more preferably 15 to 38 parts by weight, based on 100 parts byweight of the poly lactic acid (A). The content of the aliphaticdicarboxylic acid ester-containing plasticizer (DA) is commonly 8 to 35parts by weight, preferably 10 to 30 parts by weight, and morepreferably 12 to 27 parts by weight, based on 100 parts by weight of thepoly lactic acid (A). The dicarboxylic acid ester-containing plasticizer(D) having a content of less than 8 parts by weight is unlikely toprovide flexibility, and the plasticizer having a content of 40 parts byweight or more causes plate out and interferes with crystallization ofthe poly lactic acid to remarkably reduce the heat resistance.

[Crystallization Accelerator (E)]

The resin composition of the present invention may include anothercrystallization accelerator (E) in addition to the tetrafluoroethylenepolymer (C). The crystallization accelerator (E) is not specificallylimited as long as it has a crystallization acceleration effect, but itis desirable to select a substance having a crystal structure that hasan interplanar spacing similar to that of the crystal lattice of thepoly lactic acid (A). This is because a substance including a crystallattice having an interplanar spacing more similar to that of thecrystal lattice of the poly lactic acid (A) has a higher effect as acrystal nucleating agent for the poly lactic acid (A). Examples of sucha crystallization accelerator (E) include organic substances such asmelamine polyphosphate, melamine cyanurate, zinc phenylphosphonate,calcium phenylphosphonate, and magnesium phenylphosphonate and inorganicsubstances such as talc and clay. Among them, zinc phenylphosphonate ispreferred because it has the interplanar spacing most similar to theinterplanar spacing of the poly lactic acid (A) and can provide a goodcrystallization acceleration effect.

A commercially available crystallization accelerator (E) may be used.Examples of commercially available zinc phenylphosphonate include“ECOPROMOTE” manufactured by Nissan Chemical Industries, Ltd.

The content of the crystallization accelerator (E) is commonly 0.1 to 5parts by weight based on 100 parts by weight of the poly lactic acid(A). The content is preferably 0.3 to 3 parts by weight in order tofurther accelerate the crystallization and to maintain the biomassdegree. The accelerator having a content of less than 0.1 part by weightis unlikely to accelerate the crystallization, and the acceleratorhaving a content of more than 5 parts by weight cannot achieve effectscorresponding to the amount added and reduces the biomass degree.

The poly lactic acid (A)-containing resin composition may includevarious additives as necessary as long as the object of the presentinvention is not impaired. Examples of such additives include knownantioxidants, ultraviolet absorbers, plasticizers, stabilizers, releaseagents, antistatic agents, colorants, and drip inhibitors.

[Mechanical Properties]

As the index of flexibility of the film or sheet of the presentinvention, the tensile elongation at break and the residual stress ratiowere determined.

The film or sheet of the present invention preferably has a tensileelongation at break of 100% or more that is determined in accordancewith the test method of “Plastics-Determination of Tensile Properties”in Japanese Industrial Standard K7161. Furthermore, it preferably has aresidual stress ratio of 40% or less at a displacement of 10% inaccordance with the test method. A film or sheet having a tensileelongation at break and a residual stress ratio within the ranges can beflexible and relax stress during drawing.

The film or sheet of the present invention having a flexibility and aresidual stress ratio within the ranges can be achieved by limiting eachcontent of the poly lactic acid (A), the acidic functionalgroup-modified olefinic polymer (B), the tetrafluoroethylene polymer(C), and the dicarboxylic acid ester-containing plasticizer (D) ofGeneral Formula (1) within the range defined by the present invention.In particular, it is important to limit the content of the dicarboxylicacid ester-containing plasticizer (D) within the range defined by thepresent invention.

[Heat Deformation Rate]

The heat deformation rate of the film or sheet of the present inventionis determined in accordance with the heat deformation test in JapaneseIndustrial Standard C3005.

The film or sheet of the present invention preferably has a deformationrate of 40% or less under a load of 10 N for 30 minutes in a temperatureenvironment of 120° C.

[Relative Crystallization Rate]

The relative crystallization rate of the film or sheet of the presentinvention is calculated using Equation (I) from the amount of heat ΔHcat the exothermic peak associated with crystallization of a sample ofthe film or sheet in a temperature rise process after film formation andthe amount of heat ΔHm associated with the subsequent melting that aredetermined by DSC.

Relative crystallization rate (%)=(ΔHm−ΔHc)/ΔHm×100   (I)

The film or sheet of the present invention preferably has a relativecrystallization rate of 50% or more.

More preferably, the film or sheet of the present invention has adeformation rate of 40% or less under a load of 10 N for 30 minutes in atemperature environment of 120° C. in accordance with the heat test inJapanese Industrial Standard C3005 and has a relative crystallizationrate of 50% or more that is calculated from Equation (I).

In order to obtain the film or sheet of the present invention having adeformation rate of 40% or less and a relative crystallization rate of50% or more, it is important to limit each content of the poly lacticacid (A), the acidic functional group-modified olefinic polymer (B), thetetrafluoroethylene polymer (C), and the dicarboxylic acidester-containing plasticizer (D) of General Formula (1) within the rangedefined by the present invention, in particular, to limit the content ofthe tetrafluoroethylene polymer (C) and the content of the dicarboxylicacid ester-containing plasticizer (D) within the ranges defined by thepresent invention. In order to achieve the film or sheet of the presentinvention having a deformation rate of 40% or less and a relativecrystallization rate of 50% or more, it is also important to employ, asthe method for manufacturing the film or sheet of the present invention,a manufacturing method (described later) that includes forming a filmfrom a poly lactic acid (A)-containing resin composition by melt filmformation, in which the resin composition during the melt film formationhas a temperature between a temperature 15° C. higher than acrystallization temperature (Tc) of the resin composition in atemperature drop process and a temperature 5° C. lower than a meltingtemperature (Tm) in a temperature rise process and/or the melt filmformed resin composition is cooled and solidified after acrystallization accelerating step between a temperature 25° C. lowerthan a crystallization temperature (Tc) of the resin composition in atemperature drop process and a temperature 10° C. higher than thecrystallization temperature (Tc) [preferably between a temperature 10°C. higher than the crystallization temperature (Tc) and a temperature10° C. lower than the crystallization temperature (Tc)].

The film or sheet of the present invention may be used for applicationssimilar to those of common films or sheets, but in particular, can besuitably used as a base of a pressure-sensitive adhesive film or sheet.

[Method for Manufacturing Film or Sheet]

The method for manufacturing the film or sheet of the present inventionis not necessarily limited and is preferably a method of forming a filmfrom the poly lactic acid (A)-containing resin composition by melt filmformation. For example, the film or sheet of the present invention canbe manufactured by preparing the poly lactic acid (A)-containing resincomposition including each component that is homogeneously dispersed bya continuous melt kneader such as a twin screw extruder or a batch meltkneader such as a pressure kneader, a Banbury mixer, and a roll kneader,then by forming a film from the resin composition by an extrusion methodsuch as a T-die method and an inflation method, calendering, polishing,or the like, and by cooling and solidifying the film. The melt filmformation is preferably a technique of forming a film having a desiredthickness by passing the melted resin composition through a spacebetween two metal rolls, and is particularly preferably calendering andpolishing.

The thickness of the film or sheet of the present invention is properlyadjusted depending on the intended use, but is commonly 10 to 500 μm,preferably 20 to 400 μm, and particularly preferably 30 to 300 μm.

When the poly lactic acid (A)-containing resin composition is formedinto a film by the melt film formation, the temperature of the resincomposition during the melt film formation (hereinafter, referred to asthe resin temperature during the melt film formation) is not necessarilylimited, but is preferably between a temperature 15° C. higher than acrystallization temperature (Tc) of the resin composition in atemperature drop process and a temperature 5° C. lower than a meltingtemperature (Tm) in a temperature rise process. The adjustment to such atemperature accelerates the crystallization of the poly lactic acid (A)and readily provides the heat resistance to the film or sheet of thepresent invention.

For example, when the resin composition is melted to form a film bycalendering, the temperature of the resin composition during thecalender rolling (corresponding to the resin temperature during the meltfilm formation) is adjusted to between a temperature 15° C. higher thanthe crystallization temperature (Tc) of the resin composition in atemperature drop process and a temperature 5° C. lower than the meltingtemperature (Tm) in a temperature rise process. Such rolling at amelting point or lower accelerates the oriented crystallization. Theacceleration effect on the oriented crystallization is much improved bythe combination of the tetrafluoroethylene polymer (C) with the resincomposition. The tetrafluoroethylene polymer (C) is fibrillated to forma network in the resin composition and also works as the crystalnucleating agent. It is supposed that such a synergistic effectaccelerates the oriented crystallization. Therefore, by the rollingwithin the temperature range, the film or sheet of the present inventioncan obtain a smooth surface condition as well as good heat resistancedue to the oriented crystallization acceleration effect (that is, thereduction of the relative crystallization rate is suppressed, and theincrease of the heat deformation rate is suppressed).

The method for manufacturing the poly lactic acid-containing film orsheet of the present invention may further include a step of controllinga temperature condition after the melt film formation in order toeffectively accelerate the crystallization by the tetrafluoroethylenepolymer (C). Specifically, the melt film formed resin composition may becooled and solidified after a step of accelerating the crystallization(hereinafter, also simply abbreviated to “crystallization acceleratingstep”) by once keeping the resin composition between a temperature 25°C. lower than a crystallization temperature (Tc) of the resincomposition in a temperature drop process and a temperature 10° C.higher than the crystallization temperature (Tc) [preferably between atemperature 10° C. higher than the crystallization temperature (Tc) anda temperature 10° C. lower than the crystallization temperature (Tc)].That is, the crystallization accelerating step is a step of subjectingthe melt film formed resin composition to a condition where thetemperature is controlled between a temperature 25° C. lower than acrystallization temperature (Tc) of the resin composition in atemperature drop process and a temperature 10° C. higher than thecrystallization temperature (Tc) [preferably between a temperature 10°C. higher than the crystallization temperature (Tc) and a temperature10° C. lower than the crystallization temperature (Tc)], and a step ofcapable of accelerating the crystallization of the resin compositionwhile maintaining the smooth surface condition after the melt filmformation. Examples of such a temperature control method include, butare not necessarily limited to, a method of bringing the melt filmformed resin composition into direct contact with a roll, belt, or thelike that can be heated at a predetermined temperature.

In particular, the melt film formed resin composition is desirablybrought into contact with a metal roll having a predetermined surfacetemperature from the viewpoint of constant control at a predeterminedtemperature. Hence, also in the step, the poly lactic acid(A)-containing resin composition is desirably a composition that can bereadily removed from a metal roll, and also from this viewpoint, theacidic functional group-modified olefinic polymer (B) is required to beadded.

It is preferred that the time for the crystallization accelerating stepis as long as possible. The time is not necessarily limited because itfinally depends on the crystallization degree of the resin composition,but is commonly 2 to 10 seconds and preferably 3 to 8 seconds.

In the crystallization accelerating step, even when the crystallizationtemperature (Tc) of the resin composition in a temperature drop processis changed due to, for example, the addition of another crystalnucleating agent, the maximum temperature of an exothermic peakassociated with the crystallization in a temperature drop process ispreviously determined with a differential scanning calorimeter (DSC) toconstantly give an optimum temperature condition for the crystallizationaccelerating step. At that time, the consideration to the shape changeof the film or sheet obtained by heat at the temperature is littlerequired, but the step is preferably performed at a temperature at whichthe obtained film or sheet has a heat deformation rate of 40% or less.

The method for manufacturing the poly lactic acid-containing film orsheet of the present invention is preferably a method that includesforming a film from a poly lactic acid (A)-containing resin compositionby melt film formation. In the method, the temperature of the resincomposition during the melt film formation (the resin temperature duringthe melt film formation) is between a temperature 15° C. higher than acrystallization temperature (Tc) of the resin composition in atemperature drop process and a temperature 5° C. lower than a meltingtemperature (Tm) in a temperature rise process and/or the melt filmformed resin composition is cooled and solidified after acrystallization accelerating step between a temperature 25° C. lowerthan a crystallization temperature (Tc) of the resin composition in atemperature drop process and a temperature 10° C. higher than thecrystallization temperature (Tc) [preferably between a temperature 10°C. higher than the crystallization temperature (Tc) and a temperature10° C. lower than the crystallization temperature (Tc)].

In the method for manufacturing the poly lactic acid-containing film orsheet of the present invention including the crystallizationaccelerating step, the resin composition is crystallized in thecrystallization accelerating step and then cooled and solidified. Hence,the internal stress is unlikely to remain, and the obtained film orsheet does not cause large heat shrink when it is used. Therefore, thehighly crystallized film or sheet of the present invention that isformed into a film by the manufacturing method can keep the shape tonear the melting point of the poly lactic acid and can be sufficientlyused for applications that require heat resistance and that are notpreviously applicable. The manufacturing method has large advantages ineconomy and productivity because it does not require inefficient stepsof cooling and solidifying and then heating again.

It is desirable that the method for manufacturing the poly lacticacid-containing film or sheet of the present invention including thecrystallization accelerating step is continuously carried out from themelt film formation step, the crystallization accelerating step, to thecooling and solidifying step from the viewpoint of productivity becausesuch a system shortens the treatment time. Examples of such a methodinclude methods using a calender film formation machine, a polishingfilm formation machine, and the like.

[Calender Film Formation]

FIG. 1 shows a schematic view of a calender film formation machine usedin an embodiment of the manufacturing method. Hereinafter, FIG. 1 willbe described in detail.

Between four calender rolls, a first roll (1), a second roll (2), athird roll (3), and a fourth roll (4), the melted resin composition isrolled to gradually reduce the thickness. The rolling is adjusted sothat the resin composition will have a desired thickness after the resincomposition is finally passed through between the third roll (3) and thefourth roll (4). In the case of the calender film formation, the filmformation of the resin composition from the first to fourth rolls (1) to(4) corresponds to the “melt film formation step”. Take off rolls (5)having a temperature between a temperature 25° C. lower than acrystallization temperature (Tc) of the resin composition in atemperature drop process and a temperature 10° C. higher than thecrystallization temperature (Tc) [preferably between a temperature 10°C. higher than the crystallization temperature (Tc) and a temperature10° C. lower than the crystallization temperature (Tc)] are a roll groupwith which the melt film formed resin composition (8) is initially incontact. The roll group includes one or more rolls (three rolls inFIG. 1) and removes the melted resin composition (8) from the fourthroll (4). When a plurality of take off rolls (5) is used in this mannerand the temperature of each roll can be controlled, each roll preferablyhas the same temperature but may have a different temperature within adesired temperature range. A larger number of the take off rolls (5)increases the time for isothermal crystallization and has an advantagein the acceleration of crystallization. In the case of the calender filmformation, the crystallization of the melt film formed resin composition(8) is accelerated on the take off rolls (5), and thus the step ofpassing the resin composition (8) through the take off rolls (5)corresponds to the “crystallization accelerating step”.

Two cool rolls (6) and (7) cool and solidify the resin composition (8)by passing the resin composition (8) between them and also form thesurface into a desired shape. Thus, commonly, one roll (for example, thecool roll (6)) is a metal roll that has a surface designed for providinga surface shape to the resin composition (8), and the other roll (forexample, the cool roll (7)) is a rubber roll. In Fig., each arrow meansa rotation direction of a corresponding roll.

[Polishing Film Formation]

FIG. 2 shows a schematic view of a polishing film formation machine usedin an embodiment of the manufacturing method. Hereinafter, FIG. 2 willbe described in detail.

An extruder leading end (10) of an extruder (not shown in the drawing)is placed between a heated second roll (2) and a heated third roll (3).Between the second roll (2) and the third roll (3), a melted resincomposition (8) is continuously extruded at a predetermined extrusionspeed. The extruded resin composition (8) is rolled between the secondroll (2) and the third roll (3) to have a smaller thickness. The rollingis adjusted so that the resin composition will have a desired thicknessafter the resin composition is finally passed through between the thirdroll (3) and the fourth roll (4). In the case of the polishing filmformation, the film formation of the resin composition (8) from thesecond to fourth rolls (2) to (4) corresponds to the “melt filmformation step”. Then, the film is passed through three take off rolls(5) having a temperature between a temperature 25° C. lower than acrystallization temperature (Tc) of the resin composition (8) in atemperature drop process and a temperature 10° C. higher than thecrystallization temperature (Tc) [preferably between a temperature 10°C. higher than the crystallization temperature (Tc) and a temperature10° C. lower than the crystallization temperature (Tc)] and finallypassed through cool rolls (6) and (7) to prepare a solidified film orsheet. In the case of the polishing film formation, the step of passingthe resin composition through the take off rolls (5) corresponds to the“crystallization accelerating step”.

EXAMPLES

Hereinafter, the present invention will be further specificallydescribed with reference to examples and comparative examples. Thepresent invention is not intended to be limited to them.

Abbreviations of material names used in Table 1 to be described laterare shown below.

[Poly lactic Acid (A)]

A1: Lacea (registered trademark) H-400 (manufactured by MitsuiChemicals, Inc.)

[Acidic Functional Group-Modified Olefinic Polymer (B)]

B1: maleic anhydride-modified polypropylene (weight average molecularweight=49,000, acid value=26 mg KOH/g): Umex (registered trademark) 1001(manufactured by Sanyo Chemical Industries, Ltd.)

B2: maleic anhydride-modified polypropylene (weight average molecularweight=32,000, acid value=52 mg KOH/g): Umex (registered trademark) 1010(manufactured by Sanyo Chemical Industries, Ltd.)

A component (B′) below was studied in order to be compared with thecomponent (B1) and the component (B2).

B′: unmodified low molecular weight polypropylene (weight averagemolecular weight=23,000, acid value=0 mg KOH/g): VISCOL (registeredtrademark) 440P (manufactured by Sanyo Chemical Industries, Ltd.)

[Tetrafluoroethylene Polymer (C)]

C1: polytetrafluoroethylene: Fluon (registered trademark) CD-014(manufactured by ASAHI GLASS CO., LTD.)

C2: acrylic-modified polytetrafluoroethylene: Metablen. (registeredtrademark) A-3000 (manufactured by Mitsubishi Rayon Co., Ltd.)

[Phthalate Ester-Containing Plasticizer (DP)]

DP1: butyl benzyl phthalate: BBP (manufactured by DAIHACHI CHEMICALINDUSTRY CO., LTD.), a molecular weight of 314

DP2: (2-ethylhexyl)benzyl phthalate: Santicizer 261A (manufactured byFerro Japan), a molecular weight of 370

A phthalate ester-containing plasticizer (DP′) below was studied inorder to be compared with the components (DP1) and (DP2).

DP′: bis(2-ethylhexyl)phthalate: DOP (manufactured by DIC Corporation),a molecular weight of 391

[Aliphatic Dicarboxylic Acid Ester-Containing Plasticizer (DA)]

(DAI): bis[2-(2-butoxyethoxy)ethyl] adipate: BXA (manufactured byDAIHACHI CHEMICAL INDUSTRY CO., LTD.), a molecular weight of 435

(DA2): benzyl (methoxyethoxyethyl) adipate: DAIFATTY-101 (manufacturedby DAIHACHI CHEMICAL INDUSTRY CO., LTD., registered trademark), amolecular weight of 338

A phthalate ester-containing plasticizer (DA′) below was studied inorder to be compared with the components (DA1) and (DA2).

(DA′): diisononyl adipate: W-242 (manufactured by DIC Corporation), amolecular weight of 398

[Crystallization Accelerator (E)]

E1: zinc phenylphosphonate: ECOPROMOTE (manufactured by Nissan ChemicalIndustries, Ltd.)

Example 1

The raw materials above were mixed in a compounding ratio shown in Table1 to prepare a resin composition. The resin composition was melted andkneaded with a Banbury mixer, and then subjected to calender filmformation (melt film formation) using a 4-roll inverted L calender so asto have a thickness of 100 μm. Next, as shown in FIG. 1, three rolls(take off rolls) that could be heated at any temperature were placedimmediately after the melt film formation step to arrange acrystallization accelerating step where the melt film formed resincomposition could be passed while the upper side and the lower side ofthe film alternately came in contact with the rolls. Then, the resincomposition was solidified by passing through cool rolls to prepare afilm. The temperature of the resin composition during the melt filmformation (the resin temperature during the melt film formation) wasregarded as the surface temperature of the roll corresponding to thefourth roll (4) in FIG. 1, and for the temperature of the resincomposition in the crystallization accelerating step, the surfacetemperatures of three take off rolls (5) in FIG. 1 were adjusted tosubstantially the same and regarded as the crystallization accelerationtemperature. The film formation speed was 5 m/min, and the substantialtime for the crystallization accelerating step (passage time through thetake off rolls) was about 5 seconds.

Examples 2 to 5

Each resin composition was prepared in the compounding ratio shown inTable 1 and subjected to the same operation as that in Example 1 toprepare each film of Examples 2 to 5.

Comparative Examples 1 to 7

Each resin composition was prepared in the compounding ratio shown inTable 1 and subjected to the same operation as that in Example 1 toprepare each film of Comparative Examples 1 to 7.

Each sample prepared in Examples and Comparative Examples was evaluatedin the following manner.

<Melting Temperature>

The endothermic peak temperature associated with the melting of theresin composition in a temperature rerise process after film formationwas determined by a DSC to be regarded as the melting temperature (Tm;also referred to as crystal melting peak temperature).

<Crystallization Temperature>

The exothermic peak temperature associated with the crystallization ofthe resin composition in a temperature drop process from 200° C. afterfilm formation was determined by a DSC to be regarded as thecrystallization temperature (Tc; also referred to as crystallizationpeak temperature).

<Film Formability Evaluation>

(1) Releasability: The releasability was evaluated on the melt filmformed resin composition from the fourth roll (4) in FIG. 1. The resincomposition capable of being taken off onto the take off roll (5) wasevaluated as “A”, and that incapable of being taken off onto the takeoff roll (5) was evaluated as “B”.

(2) Volatile resistance: The resin composition during film formation wasvisually observed. The resin composition without volatilization (whitesmoke) was evaluated as “A” (without), and that with volatilization wasevaluated as “B” (with).

(3) Plate out to roll: A roll surface was visually observed andevaluated as “A” for no dirt on the roll surface and as “B” for any dirton the roll surface.

The evaluation of plate out to a roll was not carried out on ComparativeExample 3 because it was not removed.

<Relative Crystallization Rate>

The amount of heat ΔHc of the exothermic peak associated with thecrystallization of the film sample in the temperature rise process afterfilm formation and the amount of heat ΔHm associated with the subsequentmelting were determined by a DSC (differential scanning calorimeter) tocalculate the relative crystallization rate using Equation (I).Comparative Example 3 was not evaluated because it was not removed.

Relative crystallization rate (%)=(ΔHm−ΔHc)/ΔHm×100   (I)

Acceptance evaluation: The film having a relative crystallization rateof 50% or more was regarded as acceptance.

The DSC used for determination of the melting temperature (Tm), thecrystallization temperature (Tc), and the relative crystallization rateand the measurement conditions were as follows.

Apparatus: DSC 6220 manufactured by SII NanoTechnology Inc.

Conditions: measurement temperature region; from 20° C., 200° C., 0° C.,to 200° C. (that is, first, measurement was carried out in a temperaturerise process from 20° C. to 200° C., then in a temperature drop processfrom 200° C. to 0° C., and finally in a temperature rerise process from0° C. to 200° C.)

Temperature rise rate/temperature drop rate: 2° C./min

Measurement atmosphere: under a nitrogen atmosphere (200 ml/min)

No exothermic peak associated with the crystallization was observed inthe temperature rerise process. Hence, it was judged that 100% of acrystallizable region was crystallized at a temperature drop rate of 2°C./min, and the validity of the equation for the relativecrystallization rate was confirmed.

<Heat Deformation Rate>

The heat deformation rate was determined in accordance with the heatdeformation test in Japanese Industrial Standard C3005. The measurementapparatus and measurement conditions used are as follows.

Apparatus: Heat deformation tester manufactured by TESTER SANGYO CO.,LTD.

Conditions: sample size: 1 mm thickness×25 mm width×40 mm length (filmswere stacked into a total thickness of 1 mm)

Measurement temperature: 120° C.

Load: 10 N

Measurement time 30 minutes (the test started without aging consideringrecrystallization)

Calculation method of heat deformation rate: The thickness T1 before thetest and the thickness T2 after the test were determined, and the heatdeformation rate was calculated using Equation (II). Comparative Example3 was not evaluated because it was not removed.

Heat deformation rate (%)=(T1−T2)/T1×100   (II)

Acceptance evaluation: The film having a heat deformation rate of 40% orless was regarded as acceptance.

<Tensile Elongation at Break>

The tensile elongation at break was determined in accordance with thetest method of Plastics-Determination of Tensile Properties in JapaneseIndustrial Standard K7161.

The measurement apparatus and measurement conditions used are asfollows.

Apparatus: tensile tester (Autograph AG-20kNG manufactured by ShimadzuCorporation)

Sample size: 0.1 mm thickness×10 mm width×100 mm length

The sample was cut out so that the direction parallel to thelongitudinal direction would be the machine direction (MD) during thefilm formation.

Measurement conditions: a chuck distance of 50 mm

-   -   a tensile speed of 300 mm/min

Acceptance evaluation: each sample was subjected to the test under theconditions above, and the elongation value at the film break wasdetermined to give the tensile elongation at break. The film having atensile elongation at break of 100% or more was regarded as acceptance.

<Residual Stress Ratio>

The residual stress ratio as the index for stress relaxation propertywas determined in accordance with the test method ofPlastics-Determination of Tensile Properties in Japanese IndustrialStandard K7161.

The measurement apparatus and measurement conditions used are asfollows.

Apparatus: tensile tester (Autograph AG-20kNG manufactured by ShimadzuCorporation)

Conditions: sample size: 0.1 mm thickness×10 mm width×100 mm length

The sample was cut out so that the direction parallel to thelongitudinal direction would be the machine direction (MD) during thefilm formation.

A chuck distance of 50 mm

A tensile speed of 300 mm/min

Measurement: The displacement was stopped when the displacement reached10%, and the film was kept at the position. The stress at the time wasregarded as 100%, and the residual stress value after 60 seconds wasrecorded to calculate the “residual stress ratio”.

Acceptance evaluation: the film having a residual stress ratio of 40% orless was regarded as acceptance.

Table 2 shows the evaluation results of each test piece of Examples 1 to5 and Comparative Examples 1 to 7 prepared based on the compositiontable in Table 1.

The evaluation results shown in Table 2 reveal that each film ofExamples 1 to 5 according to the present invention ensured flexibilitybased on a tensile elongation at break of 100% or more and a residualstress ratio of 40% or less. It is also ascertained that each film had ahigh relative crystallization rate and a suppressed heat deformationrate, and hence the heat resistance was ensured. Each film further hadgood releasability and good volatile resistance and did not cause theplate out to a roll.

In contrast, in each film of Comparative Examples 1 and 2 using a lowmolecular weight plasticizer that is not included in the dicarboxylicacid ester-containing plasticizer (D) of General Formula (1) of thepresent invention(that is, a plasticizer of General Formula (1) in whichAa and Ab include no aryl group and no oxyalkylene chain), thevolatilization of the plasticizer and the plate out to a roll wereobserved, and the tensile elongation at break and the stress relaxationproperty were insufficient. The film of Comparative Example 3 thatincluded no acidic functional group-modified olefinic polymer (3) hadpoor releasability from a roll. Each film of Comparative Examples 4 and5 that contained the dicarboxylic acid ester-containing plasticizer (D)of General Formula (1) in an insufficient amount had a poor tensileelongation at break and a poor stress relaxation property. Each film ofComparative Examples 6 and 7 that contained the dicarboxylic acidester-containing plasticizer (D) in an excess amount had a poor heatresistance. That is, in Comparative Examples 1 to 7 containing nocomponent according to the present invention or not having thecompounding ratio according to the present invention, a film satisfyingboth desired flexibility and heat resistance could not be obtained.

TABLE 1 Mate- Comper- Comper- Comper- Comper- Comper- Comper- Comper-rial Example Example Example Example Example ative ative ative ativeative ative ative name 1 2 3 4 5 Example 1 Example 2 Example 3 Example 4Example 5 Example 6 Example 7 A1 100 100 100 100 100 100 100 100 100 100100 100 B1 1.0 1.0 1.0 0.5 1.0 B2 2.0 1.0 3.0 2.0 1.0 1.0 B′ 2.0 C1 8.04.0 3.0 3.0 2.0 C2 5.0 3.0 4.0 5.0 2.0 8.0 7.0 DP1 25 20 5 DP2 35 50 DP′35 DA1 15 25 5 DA2 20 40 DA′ 20 E1 2.0 1.0 1.0 1.0 3.0 1.0 3.0 2.0 Unit:part by weight

TABLE 2 Example Example Example Example Example Comparative ComparativeEvaluation 1 2 3 4 5 Example 1 Example 2 Film thickness (μm) 100 100 100100 100 100 100 DSC date for resin Melting temperature Tm 156 158 161160 158 162 160 composition (° C.) Crystallization 122 123 125 123 122115 121 temperature Tc Setting temperature Resin temperature 150 150 150150 150 155 150 (° C.) during melt film formation Crystallizationacceleration 120 120 125 125 120 115 120 temperature Film formabilityresult Releasability A A A A A A A Volatile resistance A A A A A B BPlate out to roll A A A A A B B Relative crystallization rate (%) 65 7276 75 70 65 72 Heat deformation rate (%) 31 25 22 35 28 31 23 Tensileelongation at break (%) 320 290 250 270 330 55 60 Residual stress ratio(%) 9 18 24 21 17 52 58 Comparative Comparative Comparative ComparativeComparative Evaluation Example 3 Example 4 Example 5 Example 6 Example 7Film thickness (μm) 100 100 100 100 100 DSC date for resin Meltingtemperature Tm 159 167 165 148 151 composition (° C.) Crystallization113 118 119 115 116 temperature Tc Setting temperature Resin temperature150 155 155 140 140 (° C.) during melt film formation Crystallizationacceleration 115 120 120 115 115 temperature Film formability resultReleasability B A A A A Volatile resistance A A A A A Plate out to roll— *1 A A B B Relative crystallization rate (%) — *1 85 87 34 41 Heatdeformation rate (%) — *1 15 14 73 69 Tensile elongation at break (%) —*1 11 13 340 290 Residual stress ratio (%) — *1 64 68 8 8 *1: A filmcould not be formed became of poor releasability.

INDUSTRIAL APPLICABILITY

The film or sheet of the present invention can be used for wideapplications similar to those of common films or sheets, but inparticular, can be suitably used as a base of a pressure-sensitiveadhesive film or sheet.

REFERENCE SIGNS LIST

1 First roll

2 Second roll

3 Third roll

4 Fourth roll

5 Take off roll

6 Cool roll

7 Cool roll

8 Resin composition

9 Bank (resin puddle)

10 Extruder leading end

1. A film or sheet composed of a resin composition comprising: a polylactic acid (A); an acidic functional group-modified olefinic polymer(B) including an acidic functional group and having an acid value of 10to 70 mg KOH/g and a weight average molecular weight of 10,000 to80,000; a tetrafluoroethylene polymer (C); and a dicarboxylic acidester-containing plasticizer (D) of General Formula (1); thedicarboxylic acid ester-containing plasticizer (D) being included in anamount of 8 parts by weight or more and less than 40 parts by weightbased on 100 parts by weight of the poly lactic acid (A),

(where B is a 1,2-phenylene group or —CH₂(CH₂)_(m)CH₂— (where m is aninteger of 0 to 6); and each of Aa and Ab is independently selected from(1) to (3) (where a compound in which both Aa and Ab are (3) isexcluded): (1) C₆H₅—(Ac)— (where Ac is an alkylene group having 1 to 4carbon atoms); (2) (Ae)-(Ad-O)_(n)— (where Ad is an alkylene grouphaving 1 to 5 carbon atoms, Ae is an alkyl group having 1 to 7 carbonatoms, and n is an integer of 1 to 4); and (3) an alkyl group having 1to 14 carbon atoms).
 2. The film or sheet according to claim 1, whereinthe dicarboxylic acid ester-containing plasticizer (D) is a phthalateester-containing plasticizer (DP) selected from compounds of GeneralFormulae (2) to (6), and the phthalate ester-containing plasticizer (DP)is included in an amount of 10 parts by weight or more and less than 40parts by weight based on 100 parts by weight of the poly lactic acid(A),

(where A1 and A2 are the same or different from each other; each of A1and A2 is an alkylene group having 1 to 4 carbon atoms; A3 is an alkylgroup having 1 to 14 carbon atoms; A4 is an alkylene group having 1 to 5carbon atoms; A5 is an alkyl group having 1 to 7 carbon atoms; and n isan integer of 1 to 4).
 3. The film or sheet according to claim 1,wherein the dicarboxylic acid ester-containing plasticizer (D) is analiphatic dicarboxylic acid ester-containing plasticizer (DA) selectedfrom compounds of General Formulae (7) to (11), and the aliphaticdicarboxylic acid ester-containing plasticizer (DA) is included in anamount of 8 to 35 parts by weight based on 100 parts by weight of thepoly lactic acid (A),

(where A1 and A2 are the same or different from each other; each of A1and A2 is an alkylene group having 1 to 4 carbon atoms; A3 is an alkylgroup having 1 to 14 carbon atoms; A4 is an alkylene group having 1 to 5carbon atoms; A5 is an alkyl group having 1 to 7 carbon atoms; n is aninteger of 1 to 4; and m is an integer of 0 to 6).
 4. The film or sheetaccording to claim 1, wherein the acidic functional group included inthe acidic functional group-modified olefinic polymer (B) is acarboxylic acid anhydride group.
 5. The film or sheet according to claim1, wherein the tetrafluoroethylene polymer (C) is included in an amountof 0.5 to 15.0 parts by weight based on 100 parts by weight of the polylactic acid (A).
 6. The film or sheet according to claim 1, wherein theacidic functional group-modified olefinic polymer (B) is included in anamount of 0.1 to 10.0 parts by weight based on 100 parts by weight ofthe poly lactic acid (A).
 7. The film or sheet according to claim 1,wherein the resin composition further includes a crystallizationaccelerator (E), and the crystallization accelerator (E) is included inan amount of 0.1 to 5.0 parts by weight based on 100 parts by weight ofthe poly lactic acid (A).
 8. The film or sheet according to claim 1having a deformation rate of 40% or less under a load of 10 N for 30minutes in a temperature environment of 120° C. in accordance with heatdeformation test in Japanese Industrial Standard C3005, and having arelative crystallization rate of 50% or more calculated from Equation(I),Relative crystallization rate (%)=(ΔHm−ΔHc)/ΔHm×100   (I) (where ΔHc isan amount of heat of an exothermic peak associated with crystallizationof the film or sheet in a temperature rise process after film formation,and ΔHm is an amount of heat associated with melting).
 9. The film orsheet according to claim 1 having a tensile elongation at break of 100%or more and a residual stress ratio of 40% or less at a stretch of 10%.10. A method for manufacturing the film or sheet according to claim 1,the method comprising forming a film from a resin composition by meltfilm formation, the resin composition during the melt film formationhaving a temperature between a temperature 15° C. higher than acrystallization temperature (Tc) of the resin composition in atemperature drop process and a temperature 5° C. lower than a meltingtemperature (Tm) in a temperature rise process or the melt film formedresin composition being cooled and solidified after a crystallizationaccelerating step between a temperature 25° C. lower than acrystallization temperature (Tc) of the resin composition in atemperature drop process and a temperature 10° C. higher than thecrystallization temperature (Tc).
 11. The method for manufacturing thefilm or sheet according to claim 10, wherein the resin compositionduring the melt film formation has a temperature between a temperature15° C. higher than a crystallization temperature (Tc) of the resincomposition in a temperature drop process and a temperature 5° C. lowerthan a melting temperature (Tm) in a temperature rise process and themelt film formed resin composition is cooled and solidified after acrystallization accelerating step between a temperature 25° C. lowerthan a crystallization temperature (Tc) of the resin composition in atemperature drop process and a temperature 10° C. higher than thecrystallization temperature (Tc).
 12. The method for manufacturing thefilm or sheet according to claim 10, wherein the melt film formation isa technique of forming a film having a desired thickness by passing themelted resin composition through a space between two metal rolls. 13.The method for manufacturing the film or sheet according to claim 10,wherein the crystallization accelerating step is performed by using ametal roll.